Strictly speaking all modes of travel have an emission footprint, including walking and cycling. Moving from place to place always has its costs, although some methods of travel have a smaller impact than others.
Therefore, one of the best ways to reduce your transportation emissions is to travel less. In some cases that is hard to do since we tend to be travel obsessed in rich nations. We like to think that humans have always been travel obsessed, always wanting to see what is over the hill and around the bend.
But not all cultures across history have been this way, with some occupying the same general area over hundreds and hundreds of years without ever succumbing to Itchy Foot or Grass is Greener syndromes. Generations of people who happened to like where they were.
Even today there must be billions and billions of people that are born, live, and die without getting more than a few kilometres from home. I imagine a great deal of them are alright with that situation.